The major epithelial permeability barriers are controlled and regulated by a cascade of events that is triggered by cell-cell and cell-extracellular matrix (ECM) contacts. Anomalies of integrin regulation and function have been implicated in the etiology of various pathologic conditions, including inflammatory disorders such as inflammatory bowel disease. In addition to integrins, several classes of cell surface glycoproteins, including CD98, have been shown to participate in integrin-mediated events. Through research funded by my CCFA research award, we have demonstrated the following: i) CD98 appears to associate with beta 1 integrin, disrupting outside-in integrin signaling, which normally confers cytoskeletal organization, a critical element of barrier function (J Biol. Chem. 2001, 276(42):39282-9); and ii) a novel mechanism appears to integrate cellular events, such as adhesion and amino acid transport, and the direct binding of cell surface molecules, including CD98 and ICAM-1 (J Biol. Chem. 2003, 278(26):23672-7). In the present RO1 application we propose to explore the molecular mechanisms of these phenomena. Thus, the general aim of this proposal is to better understand the expression of glycoprotein CD98 in the intestinal epithelium and its function in the epithelial-epithelial and epithelial-matrix interactions that regulate intestinal epithelial permeability. Specific aims 1 and 2 will examine the hypothesis that CD98 is a key molecule in the regulation of intestinal epithelial permeability barriers. Specific aims 3 and 4 will examine the hypothesis CD98 and beta1 integrin cluster signaling molecules that regulate the paracellular pathway in Caco2-BBE monolayers. The project will involve a variety of biochemical and biophysical methods with an emphasis on molecular approaches. The completion of the proposal should molecularly define the functional role of CD98 in the regulation of the intestinal barrier permeability. [unreadable] [unreadable] [unreadable]